A virtual operating technique that makes it possible to operate a plurality of virtual machines each having a guest OS on a virtual machine monitor operated in one computer starts to be used. The virtual machine monitor assigns a computing resource including a hard disk drive and the like to a virtual machine.
If a cache control unit is provided on the virtual machine monitor, a cache is often filled with data accessed from a virtual machine whose access frequency is high in a least recently used (LRU) algorithm in which a cache that is not accessed for the longest time is discarded. Therefore, it is difficult to enjoy the effect of the cache in a virtual machine whose access frequency is low.